The invention relates to a projector apparatus, and more particularly to a projector apparatus which separates white light into light components of the primary colors, modulates the separated light components, and then composes the modulated light components.
There are various conventional projector apparatuses for projecting images according to image signals. These projector apparatuses are classified into a system wherein white light from a light source is passed through a full-color light modulator followed by projection, and a system wherein white light from a light source is separated into light components or the three primary colors which are passed through respective light modulators and then composed, followed by projection. The invention belongs to the latter system.
Japanese Patent Laid-Open No. 171045/1998 discloses a projector apparatus which separates light using two dichroic mirrors and composes the separated light components using a cross-dichroic prism. Technique described in this publication will be explained as a first example of prior art.
FIG. 3 is a side view illustrating the structure of the first example of the conventional projector apparatus.
The projector apparatus shown in FIG. 3 comprises a light source optical system 600, a light separating optical system 700, a light guide optical system 720, a light composing optical system 780, an projection lens 770.
Light having random polarization components emitted from a light source 611 is reflected from a concave mirror 612 and then enters first and second integrators 620, 630.
The first and second integrators 620, 630 each comprise a number of minute rectangular lenses, which have been continuously arranged in a planar matrix form, and function to homogenize the illuminance distribution of the incident light and then to output the homogenized light.
The polarization light converter 640 arranges the light, output from the first and second integrator, in a specific linear polarization direction and outputs the arranged light. This light from the light source 611 is then passed through a focusing lens 650 and a reflecting mirror 660 and is applied to irradiation areas near light valves 750, 752 and a light guide lens 730.
A first dichroic mirror 710 reflects red light and green light components among the components of the incident light, and permits only a blue light component to be passed therethrough. The transmitted blue light component is passed through a reflecting mirror 718, a condenser lens 744, and a light valve 750 in that order, and then enters a cross-dichroic prism 760.
The second dichroic mirror 712 permits the transmission of only the red light component out of the red light and green light components as the incident light, and reflects only the green light component. The reflected green light component is passed through the condenser lens 742 and the light valve 752 in that order, and then enters the cross-dichroic prism 760.
On the other hand, the red light component passed through the second dichroic mirror 720 is passed through a light guide lens 730, a reflecting mirror 722, a light guide lens 734 a reflecting mirror 724, a condenser lens 744, and a light valve 754 in that order, and then enters the cross-dichroic prism 760.
The red light, green light, and blue light components input into the cross-dichroic prism 760 are composed to form a full-color image which is then projected in an enlarged manner onto a projection screen 800 through a projection lens 770.
Thus, the projector apparatus as the first example of the prior art has a structure such that light components of the three primary colors are introduced into the second cross-dichroic prism 760 from three sides around the second cross dichroic prism 760 to compose the introduced light components.
Japanese Patent Laid-Open No. 158167/1993 discloses a projector apparatus which separates light using a cross-dichroic mirror and composes the separated light components using another cross-dichroic mirror. The technique described in this publication will be explained as a second example of prior art.
FIG. 4 is a perspective view illustrating the structure of the second example of the conventional projector apparatus.
The projector apparatus shown in FIG. 4 comprises a light source 911, a concave mirror 933, a first cross-dichroic mirror 931, reflecting mirrors 934, 935, 937, 938, 940, 941, liquid crystal panels 936, 939, 942, a second cross-dichroic mirror 932, and a projection lens 943.
Light having random polarization components emitted from the light source 911 is reflected from the concave mirror 933 and then enters the first cross-dichroic mirror 931.
The first cross-dichroic mirror 931 comprises a combination of a red transmission cross-dichroic mirror and a blue transmission cross-dichroic mirror which each are disposed on the optical axis 911x of the light source 911 so as to be inclined at 45 degrees to the optical axis 911x and to be orthogonal to each other and functions to separate white light from the light source 911 into light components of the three primary colors, red light, green light, and blue light components.
A pair of reflecting mirrors 934 and 935, a pair of reflecting mirrors 937 and 938, and a pair of reflecting mirrors 940 and 941 are disposed respectively on the optical paths of green light, red light, and blue light components to bend each of the optical paths to form a xe2x80x9c⊃xe2x80x9d shape.
The second cross-dichroic mirror 932 comprises a combination of a red reflection dichroic mirror and a blue reflection dichroic mirror which each are disposed so as to be inclined at 45 degrees to the output optical axis and to be disposed orthogonal to each other. The second cross-dichroic mirror 932 is disposed just under and adjacent to the first cross-dichroic mirror 931, and composes the green light, red light, and blue light components reflected by the reflecting mirrors 935, 938, 941 to form a full-color light which is then output.
The full-color light composed by the second cross-dichroic mirror 932 is projected as a projection image by the projection lens 943 onto the projection screen 944.
Thus, in the projector apparatus according to the second example of the prior art, the adoption of a structure, wherein the first and second cross-dichroic mirrors 931, 932 are put on top of the other respectively as upper and lower cross-dichroic mirrors so as to be adjacent to each other, has eliminated the need to provide the light guide optical system 720 in the projector apparatus according to the first example of the prior art.
The projector apparatuses according to the above examples of the prior art, however, had the following problems.
In the projector apparatus according to the first example or the prior art, the light components of the three primary colors should be introduced from the three sides around the second cross-dichroic prism 760. Therefore, the provision of the light guide optical system 720 is indispensable for the structure.
Since, however, the optical path length of the red light component passed through the light guide optical system 720 is different from the optical path lengths of the green light and blue light components not passed through the light guide optical system 720, the illuminance distribution on a light valve 733 on the optical path of the red light component is unfavorably different from the illuminance distributions on light valves 731, 732 on the light paths of the green light and blue light components. Consequently, when white is displayed on the whole projection screen, a problem of color shading occurs, that is, there is a difference in color between the center portion of the projected image on the projection screen 800 and the periphery of the projected image.
Likewise, since the quantity of the red light component incident to the projection lens 770 is different from the quantity of the green light and blue light components, when white is displayed on the whole projection screen 800, a problem of color shading occurs in the projected image on the projection screen 800.
Unlike the first example of the prior art, the projector apparatus as the second example of the prior art does not have the light guide optical system 720 and thus does not pose the above problem. Instead, however, since the structure, wherein the first and second cross-dichroic mirror 931, 932 are vertically put on top of the other, is indispensable for the projector apparatus as the second example of the prior art, a light source having a large volume should be disposed adjacent to these cross-dichroic mirrors. This poses a problem of an increased height of the projector apparatus.
Further, since the projector apparatus as the second example of the prior art does not have any optical device for homogenizing the illuminance distribution, such as integrators, in the light source section, the illuminance distribution of the projection screen 944 is heterogeneous, that is, such that the center portion is bright while the peripheral portion is dark.
Accordingly, it is an object of the invention to provide a projector apparatus which is small and thin and can produce projected images having high illuminance and having no significant color shading.
The above object can be attained by the following features.
According to the first feature of the invention, a projector apparatus comprises:
a light modulation optical system (1 in FIG. 2) which separates white light into a plurality of light components with respective wavelength bands, controls the intensity of each of said plurality of light components, and then composes the controlled plurality of light components;
a projection lens (460) for projecting the light composed in the light modulation optical system (1);
a light source optical system (100) for permitting the white light to exit therefrom, the light source optical system (100) being disposed so that the optical axis (10x) of the light source optical system (100) is displaced relative to the optical axis (200x) of the light modulation optical system (1); and
a focusing lens (150) which is disposed so that the optical axis (150x) of the focusing lens is coincident with the optical axis (200x) of the light modulation optical system (1), for focusing the light output from the light source optical system (100) and inputting the focused light into the light modulation optical system (1).
According to the second feature of the invention, a projector apparatus comprises;
a light separating optical system (200 in FIG. 2) which separates white light into a plurality of light components with respective wavelength bands;
a light guide optical system (250) for bending the optical paths of said plurality of light components, which have been output from the light separating optical system (200), so as to form a xe2x80x9c⊃xe2x80x9d shape;
a light composing optical system (400) which is disposed adjacent to the light separation optical system (200) and composes the plurality of light components output from the light guide optical system (250);
light modulators (431 to 433) which are disposed respectively on optical paths between the light separating optical system (200) and the light composing optical system (400) to control the intensity of the plurality of light components;
a projection lens (460) for projecting the light composed in the light composing optical system (400);
a light source optical system (100) for permitting the white light, which has been polarized in a specific polarization direction, to exit therefrom, the light source optical system being disposed so that the optical axis (100x) of the light source optical system (100) is displaced relative to the optical axis (200x) of the light separating optical system (200); and
a focusing lens (150) which is disposed so that the optical axis (150x) of the focusing lens is coincident with the optical axis (200x) of the light separating optical system (200), for focusing the light output from the light source optical system (100) and inputting the focused light into the light separating optical system (200). Preferably, the projector apparatus may further comprise: a first relay lens (510) disposed between the focusing lens (150) and the light separating optical system (200); and a second relay lens (521 to 523) disposed between the light separating optical system (200) and the light modulators (431 to 433).
Thus, according to the projector apparatus of the invention, the light guide optical system is provided on all the optical paths of the three primary colors so that, for all the three primary colors, the optical path length and the structure of the optical systems on the optical paths are identical Therefore, the occurrence of color shading can be prevented even at the time of the display of white on the whole projection screen.
The provision of the relay optical system can enhance the efficiency for light utilization, and thus can enhance the illuminance of projected images as compared with the projector apparatus according to the first example of the prior art.
The vertical displacement of the optical axis of the light source optical system relative to the optical axis of the light separating optical system enables the height of the projector apparatus to be reduced to the sum of the height of the light separating optical system and the height of the light composing optical system, and thus can significantly reduce the thickness of the projector apparatus as compared with the projector apparatus according to the second example of the prior art.